From bfae89abf10e3dc52504e7f7f91d5eaf8e320cd3 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Tom=C3=A1=C5=A1=20Hlav=C3=A1=C4=8Dek?= Date: Wed, 8 Aug 2012 13:42:30 +0200 Subject: [PATCH] dm: Add twserial device document Signed-off-by: Tomas Hlavacek --- doc/driver-model/UDM-twserial.txt | 47 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 47 insertions(+) create mode 100644 doc/driver-model/UDM-twserial.txt diff --git a/doc/driver-model/UDM-twserial.txt b/doc/driver-model/UDM-twserial.txt new file mode 100644 index 0000000..289416a --- /dev/null +++ b/doc/driver-model/UDM-twserial.txt @@ -0,0 +1,47 @@ +================================== +TWserial device subsystem analysis +================================== + +Tomas Hlavacek +2012-03-21 + +I) Overview +----------- + +U-Boot currently implements one common API for TWSerial devices. The interface +is defined in include/tws.h and comprises of functions: + + int tws_read(uchar *buffer, int len); + int tws_write(uchar *buffer, int len); + +The functions are implemented by a proper device driver in drivers/twserial +directory and the driver to be compiled in is selected in a Makefile. There is +only one driver present now. + +The driver depends on ad-hoc code in board specific data, namely functions: + + void tws_ce(unsigned bit); + void tws_wr(unsigned bit); + void tws_clk(unsigned bit); + void tws_data(unsigned bit); + unsigned tws_data_read(void); + void tws_data_config_output(unsigned output); + +implemented in include/configs/inka4x0.h . + +II) Approach +------------ + + U-Boot TWserial drivers exports two simple functions and therefore the conversion + of the driver and creating a core for it is not needed. It should be consolidated + with include/configs/inka4x0.h and taken to the misc/ dir. + + +III) Analysis of in-tree drivers +-------------------------------- + + 1) drivers/twserial/soft_tws.c + ------------------------------ + The driver is the only TWserial driver. The ad-hoc part in + include/configs/inka4x0.h and the core soft_tws driver should be consolidated + to one compact driver and moved to misc/ . -- 2.7.4